Chain case structure of engine

ABSTRACT

A chain case structure of an engine includes an oil pump is disposed in a chain case and driven by a crankshaft of the engine and an oil pump case. The oil pump case includes an oil strainer mounting portion, an oil suction passage communicating the oil strainer mounting portion with a pump chamber, and a chain guide portion protruding toward the one end in the crankshaft direction of the engine and extending along an outer periphery of a timing chain. The oil strainer mounting portion is disposed below the chain guide portion, the oil suction passage portion is expanded from a wall surface of the oil pump case toward the engine and extended toward the chain guide portion, and the oil strainer mounting portion and the chain guide portion are connected by the oil suction passage portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chain case structure of an engine particularly capable of preventing a timing chain of the engine from falling off or being disengaged during assembling of the timing chain.

2. Description of the Related Art

In an engine of a vehicle provided with a cam-drive structure with a timing chain and an oil pump directly driven by a crank, it is generally required to remove a cam sprocket with a chain case being mounted as it is at a time of maintenance in the market. In this removing operation, the timing chain loses its mounting tension, and it is therefore necessary to locate a member for holding the timing chain so as to prevent tooth skipping of the timing chain on a wrapping portion of a crank sprocket.

For this purpose, one of conventional techniques is a method of providing a fall-off (disengagement) preventing rib for holding a timing chain in a lower portion of a crank sprocket.

However, in a conventional structure, in order to a defect mentioned above, a fall-off preventing rib having a certain length or more is disposed on a back surface of a wrapping portion of a crank sprocket so as to cover a timing chain in a width direction only for the purpose of achieving a fall-off prevention function, which causes an increase in weight.

Furthermore, in a case where it is required to form such rib with minimum thickness, the rib takes an arcuate shape having a large area with less rigidity, and because of this reason, the rib generates radiation sound, that is, acoustic radiation efficiency becomes adversely high, constituting engine noise generation source.

In a conventional technology such as disclosed in Patent Document 1 (Japanese Utility Model Laid-Open Publication No. 56-175529), for example, an engine is provided with a front cover which is made of a material with large damping, and a reinforcing member is provided in an area counteracting an external force to thereby reduce noise.

In the structure of the Patent Document 1, it is necessary to locate a dedicated member for preventing disengagement of a timing chain, which may provide a complicated structure, thus being disadvantageous.

In another conventional technology such as disclosed in Patent Document 2 (Japanese Utility Model Laid-Open Publication No. 63-174513), a lubricating device for an engine is provided with a projecting portion (as a chain guide) at a portion on a lower side of a crank sprocket for preventing a timing chain from falling off or being disengaged.

In the structure of this Patent Document 2, the projecting portion as a chain guide is formed in an oil pump case. However, the projecting portion is provided in a cantilevered manner projecting from a wall surface of the oil pump case in the chain chamber, which may provide insufficient rigidity of the protrusion portion, increase acoustic radiation efficiency, and adversely affect engine noise or vehicle vibration. Moreover, an oil suction passage and this projecting portion are provided in different positions, and the location of these portions provides a complicated structure and configuration of the oil pump case, and hence, an oil pump, thus being also disadvantageous.

SUMMARY OF THE INVENTION

The present invention was conceived in consideration of the circumstances of the conventional art mentioned above, and an object of the present invention is to provide a chain case structure of an engine having a simplified structure of an oil pump case with considerable rigidity being maintained.

This and other objects can be achieved according to the present invention by providing, in one preferred aspect, a chain case structure of an engine having a cylinder block, a crankshaft supported by the cylinder block, a crank sprocket mounted to one end of the crankshaft, a crank gear mounted to another end thereof, and a timing chain- wound around the crank sprocket and the crank gear, the chain case structure being mounted to an axial one end of the engine crankshaft,

the chain case structure comprising:

a chain case;

-   -   an oil pump that is disposed in the chain case and driven by the         crankshaft of the engine; and     -   an oil pump case including a pump chamber and covering the oil         pump,     -   wherein the oil pump case further includes an oil strainer         mounting portion, an oil suction passage communicating the oil         strainer mounting portion with the pump chamber, and a chain         guide portion protruding toward the one end in the crankshaft         direction of the engine and extending along an outer periphery         of the timing chain wound around the crank sprocket, and     -   wherein the oil strainer mounting portion is disposed below the         chain guide portion, the oil suction passage portion is expanded         from a wall surface of the oil pump case toward the engine and         extended toward the chain guide portion, and the oil strainer         mounting portion and the chain guide portion are connected by         the oil suction passage portion.

In a preferred embodiment of the above aspect, the oil suction passage portion may be configured to have a width substantially equal to a width of the chain guide portion when the oil pump case is seen from the crankshaft direction of the engine. The oil pump case may further include a pressure regulating valve, a housing accommodating the pressure regulating valve and a fastening portion fastened to the chain case and disposed between the pressure regulating valve housing and the chain guide portion so that the chain guide portion is connected to the pressure regulating valve housing through the fastening portion. Furthermore, it may be desired that the oil strainer mounting portion and the pressure regulating valve housing are connected by a reinforcing rib that is connected to the chain guide portion through the fastening portion.

The chain case structure of an engine according to the preferred aspect of the present invention mentioned above can simplify a structure of the oil pump case arranged in the chain case and also enhance the rigidity of the chain guide portion protruding from an inner wall of the oil pump case toward the engine.

The nature and further characteristic features of the present invention will be made clearer from the following description of the preferred embodiment with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a front view of an engine provided with an chain case according to one embodiment;

FIG. 2 is a view of a chain case side seen from an interior of the engine taken along an arrowed line II-II in FIG. 1;

FIG. 3 is an enlarged view of a lower portion of the chain case in FIG. 2;

FIG. 4 is a perspective view of the lower portion of the chain case in FIG. 2;

FIG. 5 is a front view of an oil pump case provided for the engine shown in FIG. 4, for example;

FIG. 6 is a back view of the oil pump case shown in FIG. 5; and

FIG. 7 is a view showing an oil lubricating path of the engine according to the embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides an embodiment of an engine chain case having an improved structure for achieving improvement of a rigidity of a chain guide and preventing fall-off (disengagement) of a timing chain.

FIGS. 1 to 7 show a preferred embodiment of the present invention. It is further to be noted that terms “upper”, “lower”, “right”, “left” and like terms indicating direction or like are used herein by wordings written on the drawings or in an illustrated attitude.

With reference to FIG. 1, reference numeral 1 denotes a horizontal engine mounted in a vehicle. The engine 1 includes a cylinder block 2 and a cylinder head 3 which is covered by a cylinder head cover 4, is disposed at a lower portion of the engine 1.

The engine 1 is provided with a turbocharger 6 at a right side portion thereof as shown in FIG. 1, an auxiliary equipment, such as air conditioning compressor, 7 and an exhaust manifold cover 8 both in a front side portion thereof, and an oil filter 9 at a lower front portion thereof.

As shown in FIGS. 1 and 2, a crankshaft 10 is journaled on the cylinder block 2. A crank sprocket 11 and a crank gear 12 are mounted to the crankshaft 10 at a front end and a rear end, respectively.

A front camshaft 13 and a rear camshaft 14 are journaled in parallel on the cylinder head 3. A front cam sprocket 15 is mounted to the front camshaft 13. A rear cam sprocket 16 is mounted to the rear camshaft 14.

A timing chain 17 is wound around the crank sprocket 11, the front cam sprocket 15 and the rear cam sprocket 16.

In order to guide the timing chain 17 with predetermined tension, a tension side timing chain holder 18 and a loose side timing chain holder 19 are mounted to the cylinder block 2 on a front side and a rear side, respectively.

In the engine 1, as shown in FIG. 7, a chain case mounting surface 20 is formed to the front portion formed as one end portion in the axial direction of a crankshaft. A chain case 21 is further disposed to the chain case mounting surface 20 so as to cover the timing chain 17. Thus, the chain case 21 is mounted to the axial one end portion of the crankshaft of the engine 1.

As shown in FIGS. 3, 4 and 7, an oil pump 22 driven by the crankshaft 10 of the engine 1 is mounted in the chain case 21, and the oil pump 22 includes an oil pump case 26, which houses an inner rotor 23 secured to the crankshaft 10 and an outer rotor 25 that rotates around the inner rotor 23 and expands/contracts a pump chamber 24.

In the oil pump case 26, as shown in FIGS. 5 and 6, there are formed: an oil suction passage portion 29 forming an oil suction passage, which provides communication between the pump chamber 24 and an inner space of an oil strainer mounting portion 28 for mounting an oil strainer 27 disposed in the oil pan 5; a chain guide portion 30 protruding toward the front portion forming one end of the engine 1 and extending along an outer periphery of the timing chain 17 wound around the crank sprocket 11; and a shaft hole 26 c.

In the arrangement mentioned above, as shown in FIGS. 5 and 6, the oil strainer mounting portion 28 is placed below the chain guide portion 30. The oil suction passage portion 29 is expanded from a wall surface of the oil pump case 26 toward the engine 1 so as to extend toward the chain guide portion 30. The oil strainer mounting portion 28 and the chain guide portion 30 are connected by means of the oil suction passage portion 29. According to such arrangement, the chain guide portion 30 is integrally connected to the oil suction passage portion 29, thus constituting a wall of the oil suction passage portion 29.

Therefore, the chain guide portion 30 and the oil suction passage portion 29 can be communalized in the oil pump case 26, thereby simplifying a structure of the oil pump case 26. The chain guide portion 30 and the oil strainer mounting portion 28 are connected via the oil suction passage portion 29 expanded toward the engine 1, thereby improving the rigidity of the chain guide portion 30 and preventing engine noise or vibration from causing. As a result, the rigidity of the chain guide portion 30 is enhanced, thereby eliminating the provision or location of a reinforcing rib in the chain guide portion 30 and reducing sizes of the chain guide portion 30 and the oil pump case 26 themselves.

In addition, the oil suction passage portion 29 overhanging in the width direction of the timing chain 17 is disposed in a position at a certain clearance from an outer edge of a running path of the timing chain 17, thereby preventing tooth skipping under the loosed state of the timing chain 17.

Furthermore, since the location of the conventionally existing oil suction passage portion 29 can be moved to a position close to the crank sprocket 11, this oil suction passage portion can be used as a holding member of the timing chain 17, thus minimizing the increasing in weight while allowing addition of a chain holding function.

Still furthermore, since the oil-suction passage portion 29 has a certain or more sectional area than that in conventional structure, the passage portion can be naturally made larger section modulus than the conventional fall-off prevention rib, thus providing a relatively high rigidity and being effective in radiation noise suppression.

As shown in FIGS. 5 and 6, the construction is made such that, in an arrangement, when the oil pump case 26 is seen from the crankshaft direction of the engine 1, the oil suction passage portion 29 has a width W, which is made equal to a width W of the chain guide portion 30.

According to such arrangement of the oil suction passage portion 29 and the chain guide portion 30 having the common width W, the entire lower portion of the chain guide portion 30 having an arcuate rib shape and the oil suction passage portion 29 can be connected, thereby enhancing rigidity of the chain guide portion 30.

Furthermore, since the oil strainer mounting portion 28 is formed to be wider than the oil suction passage portion 29 and the chain guide portion 30, the location of the oil strainer mounting portion 28 can prevent or suppress the oil suction passage portion 29 and the chain guide portion 30 from being deformed.

Still furthermore, as shown in FIGS. 3, 4 and 7, the oil pump case 26 is provided with a pressure regulating valve housing portion 32 vertically arranged so as to house a pressure regulating valve 31, and a plurality of fastening portions 33 to be fastened to the chain case 21. One of the fastening portions 33 is disposed between the pressure regulating valve housing portion 32 and the chain guide portion 30, and accordingly, the chain guide portion 30 is connected to the pressure regulating valve housing portion 32 through the fastening portion 33.

According to such connection by means of the fastening portion 33, the rigidity of the chain guide portion can be enhanced.

The oil strainer mounting portion 28 and the pressure regulating valve housing portion 32 are connected by a slanting reinforcing rib 34, which is connected to the chain guide portion 30 through a fastening portion 33.

According to such connection and arrangement, the rigidity of the oil strainer mounting portion 28 can provide further improved rigidity, thus being advantageous. Further, since the reinforcing rib 34 is connected to the fastening portion 33, and the reinforcing rib 34 and the chain guide portion 30 are connected via the fastening portion 33, it is possible to connect the chain guide portion 30 to the pressure regulating valve housing portion 32 and to the oil strainer mounting portion 28 through the reinforcing rib 34 and the fastening portion 33, thereby further enhancing the rigidity of the chain guide portion 30.

As shown in FIG. 7, the oil discharged from the pump chamber 24 in the oil pump 22 passes from the pressure regulating valve 31 through the oil filter 9 and is then supplied from an oil supply passage portion 35 to the respective portions in the engine 1 to which it is required to supply the oil.

As mentioned above, according to the preferred embodiment of the present invention, the chain guide portion is provided integrally with the oil pump case, and the oil suction passage portion expanded toward the engine is connected to the lower portion of the chain guide portion to thereby connect, to each other, the chain guide portion, the oil suction passage portion, and the oil strainer mounting portion, thereby enhancing the rigidity of the chain guide portion.

It is further to be noted that substantially the same advantageous effects may be achieved by disposing a relief valve housing portion below a crank sprocket.

The chain case structure of the engine according to the present invention may be applied to various vehicles.

It is to be noted that the present invention is not limited to the described embodiment, and many other changes and modifications may be made without departing from the scopes or sprits of the appended claims. 

1. A chain case structure of an engine having a cylinder block, a crankshaft supported by the cylinder block, a crank sprocket mounted to one end of the crankshaft, a crank gear mounted to another end thereof, and a timing chain wound around the crank sprocket and the crank gear, the chain case structure being mounted to an axial one end of the engine crankshaft, the chain case structure comprising: a chain case; an oil pump that is disposed in the chain case and driven by the crankshaft of the engine; and an oil pump case including a pump chamber and covering the oil pump, wherein the oil pump case further includes an oil strainer mounting portion, an oil suction passage communicating the oil strainer mounting portion with the pump chamber, and a chain guide portion protruding toward the one end in the crankshaft direction of the engine and extending along an outer periphery of the timing chain wound around the crank sprocket, and wherein the oil strainer mounting portion is disposed below the chain guide portion, the oil suction passage portion is expanded from a wall surface of the oil pump case toward the engine and extended toward the chain guide portion, and the oil strainer mounting portion and the chain guide portion are connected by the oil suction passage portion.
 2. The chain case structure of an engine according to claim 1, wherein the oil suction passage portion is configured to have a width substantially equal to a width of the chain guide portion when the oil pump case is seen from the crankshaft direction of the engine.
 3. The chain case structure of an engine according to claim 2, wherein the oil pump case includes a pressure regulating valve, a housing accommodating the pressure regulating valve and a fastening portion fastened to the chain case and disposed between the pressure regulating valve housing and the chain guide portion so that the chain guide portion is connected to the pressure regulating valve housing through the fastening portion.
 4. The chain case structure of an engine according to claim 3, wherein the oil strainer mounting portion and the pressure regulating valve housing are connected by a reinforcing rib that is connected to the chain guide portion through the fastening portion. 